This circuit was found in a 90s Popular Electronics. It is used for the acoustic transmitters of 40 kHz, as several found in this section. Transistors support current equivalents.
This circuit was found in an old documentation and can be powered by a solar panel. The touch...
This simple circuit can be used on both 110V and 220V mains. We find it in an 80's Electronic...
This circuit was found in a 1980s instrumentation publication and can be applied to virtually any...